1. Field
The present disclosure relates to a sheet material feeding device used for an image forming apparatus such as a copier, a printer, a facsimile, or a multifunction apparatus thereof, and an image forming apparatus including the same. In particular, the present disclosure relates to a sheet material feeding device having a lift up/down mechanism for lifting up/down stacked sheet material, and an image forming apparatus including the same.
2. Description of Related Art
An image forming apparatus is equipped with a sheet feed cassette in which paper sheets are stacked, in a detachable manner. When the sheet feed cassette becomes empty, a user draws out the sheet feed cassette from the image forming apparatus, supplies paper sheets and attaches the cassette to the image forming apparatus again. In addition, the image forming apparatus includes a lift up/down mechanism that lifts up the paper sheets stacked on a sheet stacking member toward a pickup roller so that the uppermost surface of the paper sheets contacts with the pickup roller. This lift up/down mechanism lifts up the sheet stacking member on which the paper sheets are stacked by driving force of a lift up/down motor.
In an image forming apparatus of a first related art, when the sheet feed cassette is attached to the image forming apparatus, the lift up/down motor is driven to lift up the sheet stacking member. A detecting member constituted of an optical sensor detects that the uppermost surface of the paper sheets on the sheet stacking member has reached a predetermined position, and then the lift up/down motor is stopped so that the sheet stacking member is stopped. Thus, the pickup roller contacts with the uppermost surface of the paper sheets on the sheet stacking member so that the pickup roller can feed the uppermost paper sheet.
In the image forming apparatus of the above-mentioned first related art, if the lift up/down of the sheet stacking member is blocked by an obstacle or the like so that the sheet stacking member cannot be lifted up or down, the sheet stacking member may be damaged. In addition, because the uppermost surface of the paper sheets on the sheet stacking member does not reach the predetermined position, the lift up/down motor continues to drive. As a result, if the lift up/down motor is a blush motor, overcurrent may flow in the motor so that a problem of a coil break may occur.
Therefore, there is known an image forming apparatus of a second related art that can solve the above-mentioned problem. The image forming apparatus of the second related art includes a reach detection means that detects that a sheet stacking means reaches an end position of a lift-up range, and a lift up/down means that urgently stops lifting up/down of the sheet stacking means if the reach detection means does not detects the sheet stacking means within a predetermined time set by a count means when the sheet stacking means is lifted up/down. With this structure, if the lift up/down of the sheet stacking means is blocked by an obstacle or the like, the lifting up/down of the sheet stacking means is stopped urgently so that breakage of the sheet stacking means or damage to the obstacle can be reduced.
The image forming apparatus of the second related art has a structure for urgently stopping lifting up/down of the sheet stacking means if the reach detection means does not detects the sheet stacking means within a predetermined time in order to reduce breakage of the sheet stacking means or damage to the obstacle. However, with this structure, if the reach detection means is broken and does not work normally, the lift up/down means cannot be stopped, and hence there is a problem that an actuator such as a motor of the lift up/down means continues to drive.